base: Add AsList() function to Value API.

chrome/test/automation/javascript_message_utils.h

Index: chrome/test/automation/javascript_message_utils.h
diff --git a/chrome/test/automation/javascript_message_utils.h b/chrome/test/automation/javascript_message_utils.h
index e4b61f4d9961f222f192336398e99dd2dc185cf8..1ccdc17efff0f0a8983f7d82799337ab2f1b4d09 100644
--- a/chrome/test/automation/javascript_message_utils.h
+++ b/chrome/test/automation/javascript_message_utils.h
@@ -51,11 +51,11 @@ struct ValueConversionTraits<std::vector<T> > {
     }
     return value;
   }
-  static bool SetFromValue(const Value* value, std::vector<T>* t) {
-    if (!value->IsType(Value::TYPE_LIST))
+  static bool SetFromValue(Value* value, std::vector<T>* t) {
+    ListValue* list_value = value->AsList();
+    if (!list_value)
       return false;
 
-    const ListValue* list_value = static_cast<const ListValue*>(value);
     ListValue::const_iterator iter;
     for (iter = list_value->begin(); iter != list_value->end(); ++iter) {
       if (!ValueConversionTraits<T>::CanConvert(*iter))